Aircraft gun port opening and closing device controlled by gun temperature



R. R. BEACHLER, JR., ETAL Aug. 26, 1952 AIRCRAFT GUN PORT OPENING ANDCLOSING DEVICE coNTRoLLED BY GUN TEMPERATURE 2 SHEETS-SHEET 1 Aug 261952 R. R. BEACHLER, JR., ET AL 2,608,134

AIRCRAFT GUN PORT OPENING AND CLOSING DEVICE CONTROLLED BY GUNTEMPERATURE Filed April l5, 1950 2 SHEETS--SHEET 2 Patented Aug. 26,1952 AIRCRAFT GUN PORIT OPENING AND CLOYS- ING DEVICE CONTROLLED BY GUNTEM- PERATURE Robert R.. Beachlex', Jr., Santa Monica, and John M.Oberholtzer, Los Angeles, Calif., assignors to the United States ofAmerica as represented by the Secretary of the Air Force ApplicationApril `13, 1950, Serial No. 155,721

(c1. ssa-37.5)

4 Claims. 1 In high speed aircraft, it has been found desirable top-rovide closures for the gun blast tube opening. If such openings werenot closed while the guns were not in operation, a serious decreaseinaerodynamic efficiency would be caused by the i open ports. On theother hand, if such ports are closed while a cartridge is being red froma gun, serious disruption of the airplane structure may occur, whichmayconceivably lead to the loss of the airplane and: its personnel.

Y One object of the present invention is to' provide a device which`will open the gun ports when the gun mechanism is actuated.

Another object of the invention is to provide a mechanism that willclose the gun por-ts after the gun has ceased to lire, but will keepthem open so long asthere is any danger of a heat-induced explosivedischarge resulting from leaving a cartridge in a hot barrel chamber.Such discharge is commonly known as a cook-off.

Another object of the invention is to provide a device of the abovecharacter in which the rate of cooling of the device may be synchronizedwith the rate of cooling of the gun barrel, particularly the chamberthereof, both when the ship is in the air and when it is on the ground.The two rates of cooling ,are greatly different in such case.

Another object is to provide a device of the above character which doesnot employ thermocouples. ThermocouplesA have been found to beunreliable inthis kind of duty, due to severe vibrationl to whichtheguns and other parts of the airplane are subjected.

The present arrangement, briey described, provides such a controlwherein an electrical unit comprising a thermal computing relay (ThomasA. Edison, Inc. Model 501) is utilized to simulatev the heating andcooling rates of the guns. The relay has a pair of contacts, which arenormally closed, one of which is mounted on a bi-metal strip which iswound with a heating coil. This heater is energized concurrently withthe ring of the guns. As ring continues,;the bi-metallic element isheated until contact is broken. Such action de-energizes thedoor-closing circuit but does not interrupt ring or cease heating thebimetallic element. The heat transfer of the unit occurs at a ratecomparable to the cooling of the guns and upon cessation of firing thebi-metallic Ielement cools. Resumption of firing may, however, furtherheat thebi-metal strip and prolong the cooling period required beforethe doors will close. In addition to the above mentioned bimetal stripand heater, thexed contact is carried on a second bi-metallic memberwhich compensates for over-alltemperature variations with-i in the unit(not shown). The entire assembly is inclosed in a vacuum-tube-envelope,whereby the desired slow cooling-rate is obtained.

The thermal computing relays of the kind de scribed are included in thesystem disclosed. One of these is comparable to the ground coolingratefor the guns, while the other is arranged to simulate the cooling-rateVwhile the aircraft is in the air. The relay contacts are adjusted toopen before the gun temperature rises into the critical zone where thereis danger of a cook-oli, therefore preventing the door-closing mechanismfrom being actuated.- These contacts are held open until the dangerhaspassed and the temperature has been reduced below a safe limit whereuponthe normal actuation of the doors is resumed. An additional time delayrelay for power control is provided. It tends Ito minimize the elTectsof vibration and marginal contact conditions.

Referring -now to the accompanying drawings, Fig. 1 is a schematicdiagram showing the electric circuit through which the objects of theinvention are achieved. The relays, switches, etc., are shown in theirnormal positions i. e. those assumed when no current is flowing in thecircuit.

Fig. 2 is a fragmentary View of an airplane in side elevation, to whichthe invention has been applied. An access doorA is shown open, throughwhich opening the guns may be seen.

I0 is a gun-port door closing actuator or mechanism and Il is a gun-portdoor opening actuator or mechanism. These are not further describedbecause they are conventional in various forms. One form is illustratedin Patent 2,428,359 as element 86, Figs. '7 and 8 of that patent. In thepresent ligure, I0 and Il are both grounded but are served by conductorsI2 and I3 from sources A and B, respectively. Current flow in conductorI2 is under the immediate control of a relay I4 coil which in turn isunder control of a second or thermal element-sensing relay I5 through alead I6.

The door `opening actuator Il and door closing actuator l0 are. 'underthe control of relay Il. The coil I8 of the relay I'I is grounded at I9.Relay coil I8 controls the 0.10 second slow-breakrelay-contacts 2| andsimultaneously relay contacts 22 which control respectively the portopening actuator Il and the door closing actuator l0 from sources of D.C. B and A respectively which may be of 28 volts.

The source B of direct current'supplies a. pair of identical thermalcomputing relays 25 and 26 which are effective respectively in the airand on CII conditions and the other wound with an electric heater coil,such heaters being indicated at k21 and 28 respectively. The heaters 2land 23' are ad- ,iusted to heat and cool at the same rate as the gunbarrel when the latter is respectively airborne with the airplane orsubstantially stationary on the ground. The Contact pairs 29 and 30 arearranged to be normally closed, i. e., when cool and to open when theheaters 27 and 28 have attained a critical temperature.

Source B supplies contact pairs 29 and 30, respectively, of theparallel-connected relays 25 and 26 with current whereby to energizerelay coil 3|; `The latter-is supplied through leads 32, 33 and`50whenthe armature 34 of an air-ground transfer relay is on thev groundcontact 36 as shown. When the relay armature 34 is in the air position,i. e., in contactvwith terminal 31, at end of lead 38, no ground thermalrelay connection is provided.

(B) The airplane is in the air and not ring,

(C) The airplane is in the air ring, and

(D) The airplane is on the ground ring.

Since the last case seldom occurs, description of thecircuit occurrenceswhichfmake itrpossible will be omitted. The remaining cases are howeverbelow described:

(A) The airplane is on the gro-und and not )integr-The relay S5 isclosed upwardly by the action of the landing gear on switch 39. Powerfrom source B is applied through the contacts 30 and 36 of the lead 33to energize the relay winding 3| of the relay I5, thereby closing thecontacts 44 to the right. As a result, power from the source B isapplied through the lead I6 to energize the winding Illa of the relay |4to close the armature thereof and thus to apply power A lswitch 39 isarranged to be open when the Y ship is on the ground orlwhen the landinggear (not shown) is lowered. A- spring 40 is provided t'o return it rtoclosed position 4when the airplane is inthe air. Ground connection isprovided by switch 39 for the relay coil 4|, energizingthe lat-` terfrom a third D. C. source C. Heating' current for the heating elements2l vand 28 of thermal relays 25 and 26, respectively, is provided.through a lead 43 from source B. Source B is connected to a set ofcontacts 44 of thel relay l5 through a lead 45. The opening mechanismcontrolv and powerrelay unit Il is connected to the thermal elementsensing relay E5 through the lea-da. A gun-ringrelay 47 may be energizedfrom source B. A gun ring switch 48 is provided to conduct current fromsource B through thesecond set of contacts 4'9 of the relay l5, lead 46,contacts 2| and lead i3, thereby completing the circuit to the gun portdoor opening mechanism I.

Referring now to Figure 2, in which actual adaptation of the justdescribed structure to an airplane is shown: In the figure, |00 is theairi plane fuselage in which there is a cabin |0I, containing'a steeringwheel |02, on which there is mounted a gun trigger or firing switch 48.The switch 48controls the firing of the machine guns |03, which aremounted in a compartment |04 closable by a door |05. The airplane isprovided with a landing gear |06, which is foldable as shown in dashedline at |07, into the wings one of which is |08. The guns |03 arearranged in a partially-shown forward framework or support |09. to4 tinto ports which are closable by gun port doors ||0 each covering a gunport H0. Each door ||0 is governed by an actuator IH, which hererepresents both the opening mechanism and the closing mechanism |0- Therelays and other electrical components 'may be contained in a box ||2which may be mounted inside the gun compartment |04.

Operation from source A through the armature 22 of relay to close thegun port doors by means of the actuator l0.

(B) The airplane is in the air cmi not firing.- In this case the switch39 is closed by the action of the spring 40 thereby energizing thewinding 4| oi' the relay 35 from the power source C, which closes therelay armature 34 downwardly. Consequently, power from source B isapplied through the contacts 29 of the air computing relay 25 throughthe lead'' to the switch contact 3l from which it passes through 'theleadl 50 and the relay winding 3| to continue the energization thereofand the retention ofthe switch contacts 413 to the right and hencecontinues to energize the winding |4a of the relay |4 to hold closed thegun port doors by means of the actuator |i.

(C) The airplane is in the air, -Jring.-The switch 39 is held closed bymeans of the spring 40, the firing switch 48 is closed, power fromsource B is applied through the switch and through the lead 43 to theheating elements 21 and 28, which are in parallel, to ground.' While theheating elements 2l and 28 are initially ener-l gized, the closedcontacts 29 and 30 open after a critical temperature is reached. Uponseparatdelay.

ing, contacts 29 de-energize the relay winding 3| of relay |5, therebyCausing the 'contacts 44 to close to the left. Power from the source Bis then able to flow through the switchv 48, the leadv 43, the rightVhand movable contact 49 of the relay I5 to the lead 43 to energize thewinding I8 of the relayell to armature 22 to so interrupt theapplication of power from source A vialead 5| to the armature of therelay I4. The winding |4a of -relay le is now de-energized upon lthede-energization of relay winding 3|. Power from source B is also appliedfor 0.10 second across the relay armaturev 2| to actuate mechanism toopen the gun ports. The gun ports are held open by mechanism Il, as longas the switch 48 is held closed'and 25 seconds longer, due to thecontinued heating of heating elements 21 and 2B. After 0.10 second, therelay winding I8 opens the contacts 2| and 22 of the armature of relayThe gun port doors remain open during ring due to mechanism 25 secondsafter cessation of firing gun port closing mechanism 0 will operateprovided critical temperature has not been reached. If criticaltemperature has been reached contact 29 is open, thereby delayingclosing of gun port doors until a safe (non cook-off) temperature hasbeen reached. After safe temperature has been reached due to cooling,contact 29v closes and doorswill close after normal l25second What weclaim is:

1. A gun port door controlling mechanism including actuating means foropening and closing ra gun port door, Ia source of electric power, a rstcircuit for energizing said actuating mechanism in `door openingdirection, a gun-trigger-actuated switch for 'controlling said firstcircuit, a second circuit for energizing said actuating mech-anism in'the door closing direc-tion, a thermal time delay relay for controllingsaid second circuit upon release of said trigger iactuated switch andheater means energized by said trigger-actuated-switch for varying thetime -delay of said thermal relay in energizing said second circuitproportional to the time duration of closure `of said trigger-.actuatedswitch.

2. A control Idevice for controlling aircraft gun Iport door actuatingmechanism comprising in combination with said actuating mechanism anelectric circuit including a -source of Vpower for energizing the dooractua-ting mechamsm in the opening direction, a trigger switch forcontrolling the energizing of said cir-cuit, a second circuit includinga power source for energizing said door actuating mech-anism in theclosing direction, a thermal time del-ay relay in said second circuitcontrolling the energization of said second circuit, said thermal relayhaving a pair Iof relatively movable circuit-controlling contacts,thermally responsive means for moving 'the contacts, :and heater meansenergized under the control of said trigger switch to cause saidthermally `responsive means to move said contacts in one directionduring closure oi the trigger switch, the cooling rate of said thermallyresponsive means being equivalent to the cooling rate of airplane typemachine guns after firing so that said second circuit cannot beenergized by said contacts until the rthermally responsive means hascooled to :a predetermined temperature.

3. In combination in a device ior opening and closing the doors of a guncompartment having one or more guns in said compartment, a door openingactuator, an electric circuit energizing said actuator, a slow breakrelay in said circuit,

,a door closing actuator, an elec-tric circuit energizing said actuator,a pai-r of thermal computing relays selectively included in saidcircuit, one relay having the same cooling rate as possessed by the gunit serves rwhen in flight in an airplane,

til

the other 'the same cooling rate :as the gun after it is red when in thesame airplane on the ground, a switch common to both circuits, saidswitch being closed by the landing gear of the airplane when theairplane is on the ground, a relay for including the ground thermalcomputing relay in the circuits when said switch is closed and the :airthermal `computing relay in Ithe circuits when the switch is open, atrigger switch and a safety switch for the gun, said switches beingincluded in both of the foregoing circuits to control the output ofeither circuit to the gun.

4. In a device for opening and closing the doors of a gun compartment inan -airplane in accordance with the .temperature fof a gun containedtherein, said :airplane having a f-oldable landing gear, the combinationwhich comprises a door opening actuator, an electric circuit includingslow break relay means for operating said actuator by the opening ofsaid relay, ya door closing actuator, an energizing circuit therefor,relay means included in said circuit Ito energize the circuit uponclosing, a pair of -thermal computing relays selectively included insaid circuit, one computing relay containing means to control by itscooling rate which is proportional to the cooling rate of the gun whenthe latter is not airborne the energizing circuit for said door closingactuator while the airplane is on the ground, the other `computing relaycontaining means to contro-l by its cooling rate which is proportionalto the cooling rate of the gun when the latter is airborne theenergizing circuit for said door closing actuator while the airplane isin the air, and switch means controlled by the landing gear of theairplane for including the first thermal relay in said circuit when thelanding gear of said airplane is down and for including the secondthermal relay in said circuit when said landing gear 1S up.

ROBERT R. BEACHLER, JR. JOHN M. OBERHOLTZER.

REFERENCES CITED The following references are of record in the rile ofthis patent:

` UNITED STATES PATENTS Number Name Date 1,720,723 Dodge July 16, 19292,057,384 Lamb Oct. 13, V1936

